Pyrotechnic devices



Patented Oct. 8, 1946 PYROTECHN'IC DEVICES Tenney L. Davis, Norwell, Mass, assignor to Na- 'tionalFireWorkaInc Hanover, Mass, a corporation of Massachusetts No Drawing. Application January 21, 1943,

Serial No. 473,097

This invention relates to pyrotechnic compositions which burn with the production of colored smokes which are cool in the sense that they are not hot enough to set fire to dry hay or excelsior or similar readily combustible substances. The compositions may be used in the form of a loose powder or of compressed pellets, or they may be tamped or pressed into tubular or other cases in which they are to be burned; they may be used in smoke pots, which burn for a considerable period of time, or they may be used to make smoke stars to be thrown out by a Roman candle or a bursting rocket ,or an aerial bombshell. or they may be usedin Smoke puif devices which produce clouds of smoke rapidly and during short intervals of time. In other words, the various compositions to which the present invention relates may be used for the production of colored smokes, which is to say, for the production of visible effects, in any of the numerous ways which are well known to those who are skilled in the art of fireworksmaking.

Smoke pots and similar pyrotechnic devices which burn with the production of colored smokes are used for signals and for entertainment and display. The compositions with which they are filled are well known to those who are familiar with the art of making fireworks, and consist in general of mixtures of volatile colored substances with combustible-materials and oxidizing agents in such fashionthat the latter .by their burning produce heat which volatilizes the colored substances to produce colored mists, clouds, or smokes.

One familiar example of colored smoke compo. sition is the mixture of potassium .nitrate, sulfur, and realgar which gives a white light and a white smoke if it ,is used in the manner .of a Bengal light mixture, but which yields an abundant yellow smoke if it is burned under compression in a .chokecl case after being loaded on a nipple or short spindle. The smoke or gas from such an arsenic smoke pot will set fire immediately to a handful of dry hay which is placed over the orifice from which it emerges.

The most common colored smoke compositions, by which many different colors are produced, are made from mixtures of lactose and potassium chlorate with such volatile organic dyestuffs as auramine, rhodamine, chrysoidine. paranitraniline red, paranitraniline yellow, and indigo. In the manufacture of smoke pots, the compositions are generally tamped lightly, not pressed firmly, in paper or metal cylindrical cases. The cases are closed at both ends, and holes about one- 2 quarter of an inch in' diameter are :bored through the sides or the cases at intervals on ;a spiral line around them. The mixture is ignited by means of a first fire composition loaded in the first and deepest of the holes. When the smoke pot is burning, the smoke'escapes from several of the holes-and the smoke is hot enough :to set fire to dry hay, or excelsior. or shavings, for similar material on which the device may happen to be lying. After the burning is over, the case is found to be "filled with a spon'gycarbonaceous mass cemented together by some of the dyestufi which has fused but has not been burned or volatilized away. Fullersearth or-clay is sometimes added to the compositions where it serves to absorb to some extent the melted dyestuff and to prevent it from cementing the carbonaceous material together in such manner as to obstruct or restrict the free egress :of smoke; Clay yields mixtures which tend to harden if the smoke pots are kept in storage for some time; Fullers earth does not have the same undesirable eiTect. Either substance in the composition, by diluting it, makes it burn more slowly and hence with the slower evolution of heat, and smoke pots which contain them are somewhat cooler than otherwise but still produce a smoke which is so hot that it quickly sets fire to inflammable materials. V I

Pyrotechnic compositions for the production of colored smokes commonly contain 1). a material which burns, (2) a dyestuff which is vola tilized by the heat '"of this burning and thus produces the colored smoke or mist, and en: erally ('3) an incombustible material such as fullers earth the 'e'iiect of which is entirely physical as described above. I have discovered that by the'use of ammonium nitrate, which is a cool explosive in the sense that its explosion produces no visible flash, or of the cool explosive g-uanldine derivatives (guanidine nitrate, nitroguanidine, nitrosoguanidine, nitroaminoguanidine, and l.-guanyl-l-nitrosoaminoguanyltetra zene, commonly called tetracene, all of which are cool explosives by the same criterion) in the compositions, it is possible to make smoke puffs which are so cool that they will not set fire to such an easily inflammable material as ordinary tissue paper, and to make colored smoke pots which are so cool-burning that they will not set fire to dry hay placed directly over the orifice from which the smoke is emerging. It is the use of ammonium nitrate and, of the cool guanidine explosives for this purpose which I wish to claim as my invention. The cool explosive,

according to my invention, may be used either along with the other combustible material, such as meal powder, which maintains the fire in the composition and may thus serve the purpose of cooling this fire, or, since it is a combustible as well as a cool explosive, it may be used alone for maintaining a fire which while cool in the above-mentioned sense is yet warm enough to volatilize the dyestuff and to produce the colored smoke.

The advantages of this invention are in the greater safety and in the wider sphere of usefulness of pyrotechnic devices which will not start fires. Such cool-burning colored smoke pots as are made possible by the use of this invention may, for example, be used as signals'in railway work. If one is lighted and thrown from a moving train, it will not cause a fire if it happens to fall into dry grass.

' While my invention includes the use of ammonium nitrate in cool-burning colored smoke compositions, I recognize that ammonium nitrate is hygroscopic and yields mixtures which take up moisture from the air and consequently fail These compositions are suitable for use in coolburning smoke pots. The materials are powdered finely and mixed intimately, and the compositions are loaded at the hydraulic press in cylindrical tubes which are closed at the ends, bored with holes in the sides and supplied with first fire, etc., as is usual in the art. It has been found that the higher the melting point of the dyestuff the higher the pressure of loading which gives the best effect. With the compositions cited loading pressures of less than 500 pounds per square inch or of more than 900 pounds per square inch produce inferior smoke pots. Four hundred grams of either of these compositions, loaded in a cylinder 2 inches in internal diameter, yields a smoke pot which burns for 8 Or 10 minutes emitting a colored smoke which does not set fire to dry gras or excelsior. The meal powder included in the foregoing examples signifies, in this industry, a black gun powder in a state of extremely fine sub-division.

As examples of smoke puffs, intimate mixtures of 1 part of fullers earth with 15 parts of nitrosoguanidine and 5 parts of any one of the abovementioned volatile dyestuffs may be cited. Twenty grams of such a mixture loaded loosely in a package of thin paper and lighted by means of quickmatch, gives a large cloud of brilliantly colored smoke.

Having thus described my invention, whatI desire to claim as new is:

1. A pyrotechnic composition designed to produce a colored smoke, comprising a volatile colored organic compound and a cool guanidine exof my invention to colored smoke compositions which are based upon any particular ingredient in addition to the cool explosive'guanidine derivative. In other words, I wish to use the cool explosive guanidine derivatives along with the other materials, devices, and methods which are ordinarily employed in the manufacture of colored smoke compositions. I also wish to use the c001 explosive guanidine derivatives alone with the volatile dyestufis, with or without fullers earth or other inert material.

. As examples of cool-burning colored smoke compositions which illustrate the successful application of my invention, the compositions listed in the following table may be cited.

Color of Smoke Orange Orange Yellow when volatilized by the heat of combustion of said mixture, and a non-combustible diluent, said cool explosive and said diluent being present in such proportions as to so reduce the temperature at which said combustion burns that the smoke from it will notset fire to dry hay, excelsior, or the like..

4. A pyrotechnic device of the type intendedfor display, entertainment, signalling, or the like, and in which colored smoke is produced by the burning of compositions containing a volatile dye stuif, characterized by the fact that the composition is made cool burning by including in it a cool guanidine explosive, and a container in which said composition is packed under a compression of between five hundred and nine hundred pounds per square inch.

TENNEY L. DAVIS 

